Urgency, or mood-based rash action, is one of four facets of impulsivity defined in human clinical literature (Whiteside &Lynam, 2001;Cyders, Smith, Spillane, Fischer, Annus, &Peterson, 2007). An animal model of urgency may allow further understanding of the role of specific brain systems in mood-based rash action. By manipulating reward expectancy, behavioral outcomes (such as a reinforcement omission effect, or ROE) can be measured in laboratory rats (Gipson, Zentall, &Bardo, in preparation). Gipson et al. sought to develop an operant animal analogue of urgency using an operant task in rats. Animals received an initial Pavlovian component in which a conditioned stimulus (a key light) was paired with the delivery of one sucrose pellet. A terminal, operant component followed in which animals were able to repeatedly complete a fixed-ratio (FR)-10 schedule of reinforcement for one sucrose pellet. Infrequently, no sucrose pellet was delivered in the Pavlovian component (omission trials). Response rates were measured on both trial types - rates were increased during omission trials (an ROE effect). This procedure allowed individual differences in level of urgency to be quantified. The first proposed study is designed to examine the effects of omission of expected non-drug reward (sucrose pellets) on d-amphetamine self-administration in rats. The second proposed set of studies is designed to examine the cross-species generality of the ROE by examining individual differences in urgency using an analog performance task in humans, and to determine if these individual differences reflect urgency scores on the UPPS personality scale. Using a variation of the nonhuman animal procedure described above, individuals will be tested for response rates following unexpected omission of reward. Monetary reward will be used in both human studies as the non-contingent expected reward in the initial component. Subjects will be allowed to click a computer mouse on a FR-100 schedule in a terminal component, and will receive money (study 2a) or points that can be exchanged for capsules of d-amphetamine (study 2b). To better understand how to reduce risk for mood-based rash action in humans, it is important to quantify individual differences in urgency. While there is little information on the neural systems involved in human urgency, a valid animal model of rash action would provide a foundation upon which these systems can be better studied. If the neurobehavioral causes of urgency are better understood, risk can be reduced in a more effective way, and impulsivity in predisposed individuals may be reduced if drugs can be developed to specifically target these brain areas implicated in urgency. PUBLIC HEALTH RELEVANCE: Impulsivity is known to be a risk factor for various negative health-related behaviors, including drug abuse. This project will assess a behavioral model of impulsivity in both rat and human subjects to determine its usefulness in relation to personality questionnaires that are typically used to assess impulsivity in humans. This work will advance our basic knowledge about the neural mechanisms of impulsive behavior and drug abuse.